Most automobiles have an exterior surface with either raised or recessed surface profiles. Raised surface profiles, such as outer ridges, are used to accent body lines. Recessed surface profiles, such as channels, are used to accommodate moulding attachments. Should the automobile sustain damage in the vicinity of one of it's surface profiles, such damage can be difficult to repair. One of the more difficult steps in the repair process is the step of sanding the filler material used for repair to restore the correct surface profile.
This problem exists in other fields, as well. It is common for furniture to be provided with decorative surface profiles. It is also common for doors, architectural mouldings, to have decorative surface profiles.